Tree 5-25 m. Leaves thinly chartaceous to coriaceous, elliptic-oblong to lanceolate, 5-15(-16) by 2-4.5 cm, base attenuate, apex (acute-)acuminate; Inflorescences with sparse hairs 0.1-0.3 mm, sometimes glabrescent; Fruits 1-6 per infructescence, ellipsoid, 1.5-2 by 1-1.4 cm, glabrous, without lenticel-like tubercles;
Asia-Tropical: Borneo present (Brunei present, Sabah present, Sarawak present); Malaya (Peninsular Malaysia present); Sumatera (Sumatera absent), Kelantan present, Malacca present, Pahang present, Perak present, Selangor present, Trengganu present
Malesia: Peninsular Malaysia (Perak, Kelantan, Trengganu, Pahang, Selangor, Malacca), Borneo (Sarawak, Brunei, Sabah); apparently not in Sumatra (see note 3).
3 The only (sterile) specimen (bb 6479) from Sumatra may represent H. ridleyana, but it also may be H. triandra. 1 Some collections from Pahang have proportionally many 2-lobed flowers in the inflorescences. Such flowers slightly differ in a shorter androecium which is not conspicuously triquetrous but rather subellipsoid in cross section, with shorter androphore. 4 Vegetatively H. ridleyana may be confused with H. penangiana. In Borneo H. ridleyana may resemble H. oligocarpa, but the latter has distinctly raised nerves on the upper leaf surface. 2 Specimens from Peninsular Malaysia generally have less coriaceous leaves and a thicker indumentum on the leaf buds (0.4 mm) as compared with most of the specimens from Sarawak, Brunei, and Sabah. Specimens from Borneo generally occur in heath forest or kerangas, those from Peninsular Malaysia grow on ridges and hill slopes.
Ridl. 1924 – In: Fl. Malay Penins.: 60
Gamble 1912 – In: Mat. Fl. Malay Penins.: 221
J. Sinclair 1975: p. 432. – In: Gard. Bull. Sing.: 108
Warb. 2000 – In: Tree Fl. Sabah & Sarawak: 386
Burkill 1935: Diet. Econ. Prod. Malay Penins.: 1199
J. Sinclair 1958: p. 432. – In: Gard. Bull. Sing.: f. 52
W J. de Wilde 1986 – In: Gard. Bull. Sing.: 7